<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
</head>
<body>

<script type="text/javascript">
	
/*
function show(){
	var a = 20;
}
show();
alert(a);
*/

	
	
	window.window.window.onload = function(){
		var a = new String('abc');
		var b = a;
	};
	alert(a + b);//x'abcabc' o//报错
	


</script>

</body>
</html>